## General Mechanical

#### creep doesn’t converge

• Oelot
Subscriber

Hi, I'm trying to study the creep for a tensile specimen, but my solution does not converge.

I turned on Newton-Raphson residual plots to see what happen (http://www.padtinc.com/blog/overcoming-convergence-difficulties-in-ansys-workbench-mechanical-part-i-using-newton-raphson-residual-information/

I have this (the problem is on the surface where the force is applied. )

I'm thinking about the problems, maybe my Norton's creep parameters are wrong, I calculate them from a curve :

Norton Law : creep strain rate = A* sigma^n * time^m

I deduced the 1st creep parameter is  A, the second is n, and the third is m in the engineering data.
And the value I found for them are :

1st = 0,25, 2nd = 20,58 and third = 1, I put these value in the engineering data.( are they realistic ? )

NB : I did a simple tensile test, by putting a fixed  support in one side, and by applying a force in the other.

Thanks you

• peteroznewman
Subscriber

Here is a relevant post.

You don't have the equation for Norton correct. See the post I linked to.

Creep constants depend on the Units you are in.  You need different constants if you are in psi than if you are in Pa or MPa.

Here is a post about getting creep to converge.

• gopikrishna
Subscriber

i need to simulate a round bar for creep in which one end is fixed and other is applied by a tensile load. the problem is my simulation is not converging. i have tried changing substeps, applied fine mesh, rechecked creep constants and units still problem exists. please help me to sort out this problem.

https://forum.ansys.com/forums/topic/unable-to-converge-creep-simulation-in-workbench/

• peteroznewman
Subscriber